It is known that the maximum power output of a combustion turbine is achieved by heating the gas flowing through the combustion section to as high a temperature as is feasible. The hot gas, however, heats the various turbine components, such as airfoils and ring segments, which it passes when flowing through the turbine section. One aspect limiting the ability to increase the combustion firing temperature is the ability of the turbine components to withstand increased temperatures. Consequently, various cooling methods have been developed to cool turbine hot parts.
In the case of ring segments, ring segments typically may include an impingement tube, also known as an impingement plate, associated with the ring segment and defining a plenum between the impingement tube and the ring segment. The impingement tube may include holes for passage of cooling fluid into the plenum, wherein cooling fluid passing through the holes in the impingement tube may impinge on the outer surface of the ring segment to provide impingement cooling to the ring segment. In addition, further cooling structure, such as internal cooling passages, may be formed in the ring segment to facilitate cooling thereof.